The investigation into the attempted assassination of Sergei Skripal took a dramatic turn yesterday when it emerged the detective made seriously ill in the nerve agent attack was poisoned at the home of the Russian spy.

The investigation into the attempted assassination of Sergei Skripal took a dramatic turn yesterday when it emerged the detective made seriously ill in the nerve agent attack was poisoned at the home of the Russian spy.

Around 180 specially trained troops from the Royal Marines and the RAF Regiment are being deployed to safely remove potentially contaminated material from sites in Salisbury.

Detective Sergeant Nick Bailey. Photo: Getty Images

A Metropolitan Police spokesman said: "The Counter Terrorism Policing Network has requested assistance from the military to remove a number of vehicles and objects from the scene in Salisbury town centre as they have the necessary capability and expertise.

"The public should not be alarmed and the public health advice remains the same.

"The military has the expertise and capability to respond to a range of contingencies. The Ministry of Defence regularly assists the emergency services and local authorities in the UK. Military assistance will continue as necessary during this investigation."

Gavin Williamson, the UK defence secretary, said: "Our armed forces have stepped up to support the police in their investigation in Salisbury."

Detective Sergeant Nick Bailey, who is being treated in hospital, was made seriously ill after being sent to Mr Skripal's house in Salisbury.

Det Sgt Bailey was one of the first police officers to attend the house in a cul-de-sac a few hours after Mr Skripal and his daughter Yulia collapsed in Salisbury town centre.

The admission he was made ill at the house was made by Ian Blair, the former Metropolitan Police commissioner, in a BBC interview.

Asked if there were any leads in the case, Mr Blair told the 'Today Programme' on Radio 4: "There are some indications that the police officer who was injured had been to the house, whereas there was a doctor who looked after the patients in the open, who hasn't been affected at all. So there maybe some clues floating around in here."

'The Daily Telegraph' has confirmed that Det Sgt Bailey did attend the house.

The disclosure that Det Sgt Bailey was poisoned at the Skripal family home - rather than at the scene where the pair collapsed - strongly indicates that the nerve agent was administered there.

Counter-terrorism police and security services will now be investigating how the nerve agent was administered. Nerve agent is most toxic if weaponised in an aerosol spray and takes immediate effect.

The revelation that Det Sgt Bailey was poisoned at the house suggests that the Skripals may have ingested the nerve agent and will raise the possibility that Yulia Skripal had inadvertently brought some gift for her 66-year-old father from Moscow that contained the nerve agent.

Ms Skripal (33) had flown into London on Saturday, the day before the pair collapsed.

Both remain in intensive care, unconscious and fighting for their lives.

Mr Skripal was convicted of treason in 2006 and jailed for 13 years for selling secrets to MI6, which had recruited him in the 1990s. Mr Skripal, a senior intelligence officer with Russian military intelligence GRU, was pardoned in a spy swap in 2010 and settled in Salisbury.